In a major victory for the world's largest search engine, Google has reached a settlement in a nearly two-year antitrust probe by the Federal Trade Commission that leaves largely unchanged the way the company presents competitors' Web pages in its search results.

The settlement, announced Thursday, came as part of a dual FTC investigation examining allegations - brought mostly by competitors - that Google was unfairly tampering with search results to benefit its own properties. That portion of the inquiry was closed by a unanimous vote of the five-member commission.

As part of the settlement, Google promised to stop using certain smartphone patents to block competitors' mobile gadgets.

The decision was a major setback for such Google rivals as Travelocity and Microsoft that said the Mountain View company was manipulating its search to gain an unfair advantage in search results.

While advocacy groups and competitors voiced their disdain for the decision Thursday, Google chief legal counsel David Drummond wrote on the company website, "The conclusion is clear: Google's services are good for users and good for competition."

FTC Chairman Jon Leibowitz echoed those sentiments, saying FTC's settlement and decisions, which were based on the examination of more than 9 million documents from Google, will create a fairer playing field in Internet search and advertising.

Algorithm unchanged

The FTC "had to find evidence of bad behavior and a reason why we could care," said Eric Goldman, a professor of Internet law at Santa Clara University. "They couldn't. The FTC position is that they couldn't find any customer harm."

Carl Shapiro, a professor of business at UC Berkeley and a former deputy assistant attorney general in the antitrust division of the Justice Department, added, "Google got the imprimatur of the Federal Trade Commission that what they are doing is totally legitimate."

As part of the settlement, Google agreed to allow websites to opt out of "scraping" - copying content off a website - for display on Google's pages. For most Internet users, though, Web discovery happens through search, and Google is still the unquestioned dominant search engine, so a business that opted out would hamper its ability to be found on the Web.

The federal investigation did not include an examination of the Google search algorithm - one of the most secret pieces of software in the world. Google tinkers with its algorithm, which determines what results appear on the page when you search, almost daily.

"We recognize this is a dynamic industry," Leibowitz said. "We wanted to be careful before applying sanctions."

Otherwise, Leibowitz said, the FTC found that Google "didn't violate American antitrust laws." In closing its investigation into Google's tampering with search results, the FTC noted that it could reopen it any time.

Google remains under investigation for anticompetitive behavior by European Union regulators.

YouTube blocked

This is not the first time Google has raised FTC concerns. The company paid $22.5 million in August to settle allegations that it bypassed privacy settings on Apple's Safari Web browser to deliver advertisements.

That the FTC chose not to take more significant action in regard to Google's search practices is seen as bad news for competitors. Vince Sollitto, a spokesman for Yelp, one of many Web businesses that have been critical of Google's practices, called the FTC's closure of the investigation "a missed opportunity to protect innovation in the Internet economy, and the consumers and businesses that rely upon it."

Microsoft, no stranger to antitrust investigations, took a particular interest in the case. The company's general counsel, Dave Heiner, wrote in a blog post Thursday that Google continues to hamper access to its YouTube online video site on Microsoft's Windows phones.

"Just last month we learned from YouTube that senior executives at Google told them not to enable a first-class YouTube experience on Windows phones," he wrote. "Google dismisses these concerns as little more than sour grapes by one of its competitors."

FairSearch, an advocacy group representing tech giants like Oracle, Expedia, Kayak and Microsoft, derided the FTC's conclusions as "disappointing and premature."

'Abuse' stopped

On the issue of patents, Leibowitz said the settlement requires Google to offer "fair, reasonable and nondiscriminatory" terms to any company that wants to license patents that the company inherited when it bought Motorola Mobility in 2011.

"These essential patents are the cornerstone of interoperability so wireless Internet devices can talk to one another," Leibowitz said. "We stopped that abuse."